There is very limited knowledge of CSA pharmacokinetics in patients with autoimmune diseases. In this study we provided routine monitoring of whole blood CSA concentrations as a measure of CSA efficacy and toxicity. Whole blood samples were split for comparative analysis by HPLC and RIA respectively. We were able to discern the relationship between whole blood CSA concentrations as measured by the two methods of assay. Furthermore, we studied the steady state pharmacokinetics of oral CSA in 20 patients in order to determine the absorption and disposition characteristics of CSA in the patient population.